Question
In the following, find the value of the constant k so that the given function is continuous at the indicated point:
$\text{f(x)}=\begin{cases}\text{k}+1,&\text{if}\text{ x}\leq5\\3\text{x}-5,&\text{if}\text{ x}>5\end{cases}\text{at x} =5$

Answer

$\text{f(x)}=\begin{cases}\text{k}+1,&\text{if}\text{ x}\leq5\\3\text{x}-5,&\text{if}\text{ x}>5\end{cases}\text{at x} =5$We have given that function is continuous at x = 5
$\therefore\ \text{LHL}=\text{RHL}=\text{f}(5)\ ....(\text{i})$
$\text{f}(5)=5\text{k}+1$
$\text{LHL}=\lim_\limits{\text{x}\rightarrow5^+}\text{f(x)}=\lim_\limits{\text{h}\rightarrow0}(5+\text{h})$
$=\lim_\limits{\text{h}\rightarrow0}3(5+\text{h})-5=10$
Thus, using (i) we get,
$5\text{k}+1=10$
$5\text{k}=9$
$\text{k}=\frac{9}{5}$

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